What is Complete Heart Block

No impulse from atria transmitted to the ventricles. So, ventricles generate their own rhythm.

Causes of Complete Heart Block (CHB)

1. Acute CHB—Acute MI (commonly inferior).
2. Chronic CHB—
–– Progressive fibrosis of distal His-Purkinje system (Lev’s disease) in elderly.
–– Progressive fibrosis of proximal His-Purkinje system (Lenegre’s disease) in younger.

Other Causes

• Cardiomyopathy.
• Myocarditis.
• Drugs (digoxin, b-blocker, amiodarone).
• Cardiac surgery (aortic valve replacement, VSD repair).
• Radiofrequency AV node ablation.
• Infiltrative disease (sarcoidosis, amyloidosis, haemochromatosis).
• Infection (infective endocarditis, Chaga’s disease, Lyme’s disease).
• Collagen disease (SLE, Rheumatoid arthritis).
• Congenital complete heart block. It is common in child of mother with SLE (due to transplacental
transfer of anti-Ro antibody/SSA).


• Weakness, dizziness, giddiness, syncopal attack (Stokes–Adams attack).
• Breathlessness on exertion.


• Pulse—bradycardia, 20–40 beats/minute (<40 beats/min), high volume, does not increase
by exercise or injection atropine.
• BP—high systolic, normal diastolic and high-pulse pressure.
• Neck vein—cannon waves (large ‘a’ wave) may be present.
• Heart sounds—variable intensity of first heart sound.
• Murmur—systolic flow murmur.
Mechanism of Cannon Wave
When the atria contracts against closed tricuspid valve, backward pressure produces cannon

ECG Criteria

• Atrial rate more, ventricular rate <40.
• PP interval—constant.
• No relationship between P wave and QRS complex (PR looks variable, a clue).


• If the patient is symptomatic—permanent pacemaker.
• In congenital complete heart block, pulse rate is high, no pacemaker is necessary.

Stokes–Adams Attack

It is the brief attack of syncope or blackout in a patient with complete heart block due to ventricular


• Syncope or blackout with or without preceding dizziness.
• During attack—the patient is unconscious, looks pale and may have convulsion.
• If asystole persists—there may be cyanosis, pulse is absent, pupil is fixed and dilated, incontinence
of urine,
• Plantar is extensor.
• Usually, consciousness recovers rapidly followed by flushing.


• Permanent pacemaker.